An articulated seal for use with polished rod and a standard packing and/or rotary drive head assemblies is described. In particular, an articulated seal assembly or system is described which seals a rotating polished rod between high pressure internal fluids within a well and the exterior while absorbing the normal wobble motion of a rotating polished rod.
The use of a polished rod and rod string for pumping production wells is known wherein a polished rod and rod string is rotated within the tubing string of the well in order to pump oil from the well. As the polished rod is rotated by a motor at the well-head, the shaft of the polished rod must be provided with a seal system to ensure that high pressure fluids from within the well do not leak or escape at the well-head. In addition, the seal system must also prevent leaks during periods of no rotation.
In the past, various rotary seals have been incorporated into production wells to prevent both static and dynamic leakage during periods of rotation and non-rotation. In addition to basic rotation seals, advanced sealing systems have also been developed which have incorporated additional functionality within the seals including systems which absorb wobble (defined as a dynamic run-out of the polish rod) in the polished rod and the detrimental effect of that wobble on the integrity of the seals.
For example, Applicants U.S. patent application 09/433,687 describes a gimbal seal for absorbing polished rod wobble through the use of a ball and socket joint and rubber seals which allow wobble forces to be absorbed while maintaining a seal. While this design of seal was demonstrated as effective in the short-term, the long term effectiveness of this design provided non-optimal results. Accordingly, there continues to be a need for seal systems for rotating polished rods which provide a seal for both the rotational and wobble motion of a rotating polished rod within either a standard packing assembly or a rotating seal assembly and which also are effective in providing sealing during non-rotation.
In accordance with the invention, there is provided an articulated seal system comprising:
upper and lower seal supporting elements, the upper and lower seal supporting elements having respective overlapping flanges, the overlapping flanges defining a void; and
a resiliently flexible seal within the void.
In a further embodiment, the invention provides a method of assembling an articulated seal system having upper and lower seal supporting elements having respective overlapping flanges, the overlapping flanges defining a void, comprising the steps of:
(a) inserting the overlapping flange of either of the upper or lower seal supporting elements into the overlapping flange of the opposing element;
(b) stabilizing the upper and lower seal supporting elements with respect to one another; and
(c) injecting an un-cured sealing agent into the void and allowing the sealing agent to cure.
In a still further and more specific embodiment, there is provided an articulated seal system for sealing between the interior and exterior of a well comprising:
a lower seal supporting element having an inwardly projecting flange;
an upper seal supporting element having an outwardly projecting flange overlapping with the inwardly projecting flange wherein the inwardly and outwardly projecting flanges define an s-shaped void having curved surfaces between the interior and exterior of the articulated seal system; and,
a resiliently flexible seal bonded to the curved surfaces of the void.
In a still further embodiment, the invention provides a seal assembly for use at a wellhead, the wellhead having a rotating drivehead operatively connected to a rotating inner sleeve and a polished rod, the seal assembly comprising:
a lower seal assembly for sealing between the rotating inner sleeve and a stationary mount;
a bearing assembly operatively connected between the rotating inner sleeve and the stationary mount;
an articulated seal operatively connected to the rotating inner sleeve, the articulated seal having upper and lower seal supporting elements, the upper and lower seal supporting elements having respective overlapping flanges, the overlapping flanges defining a void; and a resiliently flexible seal within the void; and
a top seal assembly for sealing between the polished rod and the exterior of the wellhead.